Slideable vascular filter

ABSTRACT

A collapsible medical device for use, e.g., as a vascular filter. The device includes a mandrel having a distal end and a stop spaced proximally of the distal end. A proximal length of the mandrel extends proximally of the stop and a distal length of the mandrel extends distally of the stop. A functional element (e.g., a vascular filter) has a radially expandable body and includes a proximal slider and a distal slider. The proximal and distal sliders are slidable along the mandrel independently of one another such that the distance between the proximal slider and distal slider can be varied to effect different configurations of the functional element. In one method of using such a device, the functional element is urged distally to a treatment site by urging the mandrel distally. This causes the stop to exert a distal biasing force on the distal slider, which acts against a restorative force of the functional element to axially elongate the functional element and reduce friction between the functional element and a wall of the vessel.

FIELD OF THE INVENTION

The present invention provides a medical device which can employed in aminimally invasive medical procedure, e.g., by deploying it in a bloodvessel through a catheter. While a variety of such medical devices canbe made in accordance with the invention, the invention is particularlyuseful as a filter for use in a blood vessel or other channel in apatient's body.

BACKGROUND OF THE INVENTION

Filters can be deployed in channels or vessels in patient's bodies in avariety of medical procedures or in treating certain conditions. Forexample, rotating burrs are used in removing atheroma from the lumen ofpatients' blood vessels. These burrs can effectively dislodge theatheroma, but the dislodged material will simply float downstream withthe flow of blood through the vessel. Filters can be used to capturesuch dislodged material before it is allowed to drift too fardownstream, possibly occluding blood flow through a more narrow vessel.

Some researchers have proposed various traps or filters for capturingthe particulate matter released or created in such procedures. However,most such filters generally have not proven to be exceptionallyeffective in actual use. These filters tend to be cumbersome to use andaccurate deployment is problematic because if they are not properlyseated in the vessel they can drift to a more distal site where they arelikely to do more harm than good. In addition, these filters aregenerally capable of only trapping relatively large thrombi and are noteffective for removing smaller embolic particles from the blood stream.

The problems with most temporary filters, which are intended to be usedonly during a particular procedure then retracted with the thrombitrapped therein, are more pronounced. Even if the trap does effectivelycapture the dislodged material, it has proven to be relatively difficultor complex to retract the trap back into the catheter through which itwas delivered without simply dumping the trapped thrombi back into theblood stream, defeating the purpose of the temporary filter device. Forthis reason, most atherectomy devices and the like tend to aspirate thepatient's blood during the procedure to remove the dislodged materialentrained therein.

One promising filter design which overcomes many of these difficultiesis shown in International Publication No. WO 96/01591(the publication ofPCT International Application No. PCT/US95/08613), the teachings ofwhich are incorporated herein by reference. Generally, this referenceteaches a trap which can be used to filter particles from blood or otherfluid moving through a body vessel. In one illustrated embodiment, thistrap includes a basket 270 which can be deployed and retracted through acatheter or the like, making it particularly suitable for use inminimally invasive procedures such as angioplasty or atherectomyprocedures. The fact that this trap is optimally carried on a mandrel260 further enhances its utility as most common angioplasty balloons andatherectomy devices are used in conjunction with such mandrels. Whilethis trap is very useful and shows great promise in many commonprocedures, it may be possible to improve the ease with which it may bedeployed and/or retracted.

Some medical devices are also permanently deployed in a patient'svessel, but properly positioning these devices at the desired treatmentsite using minimally invasive techniques can be cumbersome. For example,occlusion devices can be used to occlude an arterial vessel or a septaldefect. Some of these occlusion devices may radially expand into anenlarged configuration wherein they substantially fill the lumen of thevessel or extend over the margins on either side of a septal defect.When deploying these occlusion devices through a delivery catheter,though, the friction between the occlusion device and the wall of thecatheter can make it difficult to deploy the device at a preciselyselected location. These problems are even more pronounced in longercatheters tracking through more tortuous paths.

SUMMARY OF THE INVENTION

The present invention provides a medical device which can easily bedeployed and retracted during a minimally invasive medical procedure. Inone preferred embodiment, the medical device may take the form of afilter useful in any channel of a patient's body, be it in a bloodvessel, urinary tract, or other type of vessel.

One embodiment of the invention provides a collapsible medical deviceincluding a mandrel and a functional element of any desired shape toachieve a particular end. The mandrel has a distal end and a stop spacedproximally of the distal end. A proximal length of the mandrel extendsproximally of the stop and a distal length of the mandrel extendsdistally of the stop. The functional element includes a radiallyexpandable body having a proximal slider and a distal slider. Theproximal slider is slidably carried along the proximal length of themandrel and the distal slider is slidably carried along the distallength of the mandrel. The proximal and distal sliders are slidablealong the mandrel independently of one another such that the distancebetween the proximal slider and the distal slider can be varied toeffect different configurations of the functional element.

A medical device in accordance with another embodiment of the inventionincludes a mandrel and a suitably shaped functional element. Like theprior embodiment, this mandrel has a distal end and a stop spacedproximally of the distal end. A proximal length of the mandrel extendsproximally of the stop and a distal length of the mandrel extendsdistally of the stop. The functional element of this embodiment has aradially expandable body having a radially expanded configuration andadapted to resiliently assume the radially expanded configuration in theabsence of a countervailing biasing force. The radially expandable bodyis attached to the mandrel by a proximal slider and a distal slider. Theproximal slider is slidably carried along the proximal length of themandrel and the distal slider is slidably carried along the distallength of the mandrel. The proximal and distal sliders are slidablealong the mandrel independently of one another such that the distancebetween the proximal and distal sliders can be varied to effectdifferent configurations of the body.

In one particular adaptation of the invention, the medical device has amandrel generally as described above and also includes a functionalelement. The functional element of this embodiment is formed of aresilient tubular braid which has a preferred radially expandedconfiguration but will assume a radially reduced profile upon axialelongation. Proximal and distal sliders are attached to the tubularbraid with a length of the braid extending therebetween. The proximalslider is slidably carried along the proximal length of the mandrel andthe distal slider is slidably carried along the distal length of themandrel. The proximal and distal sliders are slidable along the mandrelindependently of one another.

Yet another embodiment of the invention provides a filter system whichmay be temporarily deployed in a channel of a patient's body. Thisdevice includes a mandrel having a distal end and an enlarged diameterstop carried proximally of the distal end. A filter is formed of aresilient tubular braid and includes proximal and distal sliders. Theproximal slider is slidably carried along the mandrel proximally of thestop and the distal slider is carried along the mandrel between the stopand the distal end of the mandrel. The filter has a collapsedconfiguration wherein the sliders are spaced from one another a firstdistance along the mandrel and the filter has a first diameter. Thefilter also has an expanded configuration wherein the sliders are spaceda second, shorter distance along the mandrel and the filter has a seconddiameter. The filter's first diameter is less than its second diameter.

The present invention also contemplates a method of employing a medicaldevice in a lumen vessel. This medical device desirably comprises amandrel having a distal end and a stop spaced proximally of the distalend. It also includes a functional element, which may be formed of aresilient tubular braid and include proximal and distal sliders, withthe proximal slider being slidably carried along the mandrel proximallyof the stop and the distal slider being carried along the mandrelbetween the stop and the distal end of the mandrel. The distal end ofthe mandrel is inserted in the lumen of the vessel. The functionalelement is urged distally along the lumen to a treatment site by urgingthe mandrel distally such that the stop engages the distal slider andexerts a distal biasing force thereon. This distal biasing force actsagainst a restorative force of the functional element to axiallyelongate the functional element and reduce friction between thefunctional element and a wall of the vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of one medical device inaccordance with the invention in its deployed state;

FIG. 2 is a schematic side view of the medical device of FIG. 1, also inits deployed state;

FIG. 3 is a schematic side view in partial cross section of the medicaldevice of FIGS. 1 and 2;

FIG. 4 is a schematic side view in partial cross section of the medicaldevice of FIGS. 1 and 2, but in a partially collapsed configurationinduced by urging the mandrel distally;

FIG. 5 is a schematic side view in partial cross section of the medicaldevice of FIGS. 1 and 2, but in a partially collapsed configurationinduced by proximal withdrawal of the mandrel;

FIG. 6 is a schematic isolation view in partial cross section of themedical device of FIGS. 1 and 2, showing the relationship between themandrel, the stop and the distal slider;

FIG. 7 is a schematic side view of an alternative medical device of theinvention in its deployed state;

FIG. 8 is a schematic side view in partial cross section of the medicaldevice of FIG. 7, but in a partially collapsed configuration induced bywithdrawing the mandrel proximally within a vessel;

FIG. 9 is a schematic side view in partial cross section of the medicaldevice of FIG. 1, but in a partially collapsed configuration induced byurging the mandrel distally within a catheter;

FIG. 10 is a schematic side view in partial cross section of the medicaldevice of FIG. 1, but illustrating how the medical device may bewithdrawn using a retrieval catheter;

FIG. 11 is a schematic side view in partial cross section of a medicaldevice in accordance with another embodiment of the invention in itsdeployed state; and

FIG. 12 is a schematic perspective view of a stop of the invention whichmay be used to facilitate withdrawal of the mandrel for permanentdeployment of a medical device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 are schematic illustrations of one medical device inaccordance with the present invention. This medical device comprises afilter system 10 which can be deployed in a channel in a patient's body.As noted above, this filter can be used in any channel in a patient'sbody, including blood vessels, the urinary tract or biliary tract andairways. This filter system 10 is optimally designed to be deployed in apatient's vessel in a minimally invasive procedure, such as byintroducing the filter system into a blood vessel through an introducingcatheter (not shown in FIGS. 1 and 2).

The filter system 10 of the invention generally includes a mandrel 20and a filter 50. Conceptually, the mandrel 20 can be thought of ashaving a primary function of positioning and controlling the deploymentof the filter 50 while the filter can be considered the primarytherapeutic or functional element of the system 10.

The mandrel 20 should be fairly flexible to allow the device to bedeployed in a curving body passageway without kinking or otherwiseinhibiting suitable deployment of the filter 50. While the mandrel canbe formed of any material having any dimension suitable for the task forwhich the filter system 10 is to be employed, in most circumstances, themandrel 20 will comprise an elongate metal wire. In one particularlypreferred embodiment, the mandrel 20 is formed of nitinol, a roughlystoichiometric alloy of nickel and titanium having excellent“superelastic” properties. The use of nitinol in medical guidewires andrelated applications is well known in the art and need not be discussedin detail here. If so desired, the distal-most length of the mandrel mayinclude a flexible helically wound coil 22 extending thereover. The useof such helical coils to enhance flexibility of the distal tip is wellknown in the guidewire art.

The mandrel 20 has an enlarged diameter stop 40 attached thereto. Thestop 40 is spaced proximally from the distal tip 25 of the mandrel 20.Desirably, the stop 40 is spaced proximally of the proximal end of thehelical coil 22 of the mandrel. This permits the distal slider 60 of thefilter 50 to slide relatively freely and unencumbered along the lengthof the mandrel distally of the stop.

The stop 40 can be formed of any desired material and can be attached tothe mandrel 20 in any desired fashion. The stop should be attached tothe mandrel relatively securely, though, as the stop will be used tourge the filter 50 within the lumen of the vessel in which the system 10is to be deployed. As an example, the stop 40 may comprise a standardradiopaque marker band which has been securely crimped on the mandrel 20and/or attached to the mandrel using an adhesive or solder. The preciselength and shape of the stop 40 is not critical. The drawings illustratethe stop 40 as a relatively short cylindrical body attached about thecircumference of the mandrel. However, the stop 40 may have a morebulbous shape and could, in theory, even be formed integrally with themandrel.

The stop 40 effectively divides the mandrel into distal and proximallengths. The distal length 30 of the mandrel can be thought of as thatlength which extends distally from the stop 40 to the distal tip 25 ofthe mandrel. Likewise, the proximal portion 35 of the mandrel 20 can bethought of as comprising the length of the mandrel extending proximallyfrom the stop 40 to the proximal end of the mandrel.

The filter 50 shown in FIGS. 1-5 has an elongate, generally tubular body52 which extends from a distal slider 60 proximally to a proximal slider65. The body 52 of the filter can be formed of any material suitable forthe application at hand. In many applications, e.g., filtering bloodwithin a patient's vasculature, the filter body 52 typically comprises alength of a braided tubular fabric. The use of a tubular braid ofnitinol to make medical devices is described in some detail inInternational Publication No. WO 96/01591, the teachings of which wereincorporated above by reference. Briefly speaking though, this processcan employ a tubular braid of a fabric comprising two sets of nitinolwires wrapped helically about a mandrel, with one set of wires beingwrapped spirally about the mandrel in one direction and the other setbeing wrapped in the other direction. This braid is then placed incontact with a molding surface of a molding element which defines theshape of the desired functional element. By heat treating the fabric incontact with the molding surface of the molding element, one can createa functional element having virtually any desired shape.

The body 52 of the filter 50 desirably is made of a fairly flexible,resilient material. In particular, the filter 52 desirably has aradially expanded configuration, e.g., the shape shown in FIGS. 1-3,which the device will tend to resiliently assume in the absence of anycountervailing biasing force. A body 52 formed of a nitinol tubularbraid which has been heat set into the desired shape should suit thispurpose well.

In the filter system 10 shown in FIGS. 1-5, the body 52 of the filter 50assumes a generally tubular shape having tapered proximal and distalends. The outer diameter of the generally cylindrical middle length ofthe body 52 should be sized to substantially fill the lumen of a vesselto ensure that the filter will effectively trap any emboli which may beentrained in the patient's bloodstream. As will be discussed in moredetail below, an alternative configuration of a filter body 152 isillustrated in FIGS. 7 and 8 and medical devices intended to achievedifferent clinical objectives are shown in FIGS. 11 and 13. A variety ofother filter shapes, as well as shapes of other types of medical devicesshould be readily apparent to one of ordinary skill in the art in lightof the present teachings.

The filter 50 is attached to or carried by the mandrel 20 by means of aproximal slider 65 attached to the body 52 adjacent its proximal end anda distal slider 60 attached adjacent the distal end of the body 52. Thedistal slider 60 should be free to slide along at least a proximalportion of the distal length 30 of the mandrel while the proximal slider65 should be free to slide along at least a distal portion of theproximal length 35 of the mandrel. For reasons discussed more fullybelow in connection with FIGS. 3-5, the stop 40 of the mandreleffectively defines a limit on the range of motion of these sliders 60,65.

While each of the sliders 60, 65 should be slidable along its respectivelength of the mandrel, the sliders can take any desired shape. In theillustrated embodiments, each slider comprises a relatively thin ringwhich is carried about the mandrel. The thin ring can be attached to thebody 52 in any desired fashion, such as by crimping or swaging thefabric of the body between two layers of the ring or soldering, weldingor otherwise adhering the fabric to the ring. The structure of onesuitable distal slider is schematically illustrated in a more detailedcross section in FIG. 6. The proximal slider may have substantially thesame configuration, but is not shown in this view simply for purposes ofclarity.

In the embodiment illustrated in FIG. 6, the distal slider 60 comprisesa relatively rigid annular ring 61 having an inner component 61 a and anouter component 61 b. One or both components of the ring 61 ispreferably formed of a radiopaque material to enable a physician tobetter visualize the position of the slider 60 during a procedure. Theinner component 61 a of the ring is received within the outer component61 b and defines an annular space therebetween. The inner diameter ofthe inner component is larger than the outer diameter of the mandrel 20to facilitate sliding of the ring 61 with respect thereto. Movement ofthe slider 60 with respect to the mandrel can be further facilitated bycoating one or both of the inner surface of the inner component 61 a andthe outer surface of the mandrel 20 with a friction-reducing coating,such as Teflon or a lubricious hydrophilic coating.

A distal length of the fabric of the body 52 is received in the annularspace between the interior and exterior components 61 a and 61 b of thering. The fabric is held in place in this space in any suitable manner,e.g. by means of a suitable solder or adhesive or by crimping the fabricbetween the inner and outer components. FIG. 6 schematically illustratesboth approaches, with the fabric being frictionally grasped between thetwo components of the ring 61 and held in place by a weldment oradhesive connection 62 at the distal end of the ring.

FIGS. 3-5 schematically illustrate the filter system 10 of FIGS. 1 and 2in partial cross section. In particular, the filter 50 is shown in crosssection while the mandrel 20 and its components are shown in side view.This is intended to better illustrate the interaction of the stop 40 ofthe mandrel and the sliders 60, 65 of the filter 50.

In FIG. 3, the filter 50 is shown in its radially expandedconfiguration, which it will tend to assume in the absence of anycountervailing biasing force. The stop 40 of the mandrel is positionedwithin the body 52 of the filter and is not exerting any biasing forceon either of the sliders 60, 65.

In this configuration, the mandrel 20 can be moved proximally anddistally with respect to the filter 50 without substantially affectingthe shape or position of the filter. The limits of this range of freemovement of the mandrel with respect to the filter are generally definedby the relationship between the stop 40 and the sliders 60, 65. Inparticular, the mandrel can be moved from a distal position wherein thestop 40 abuts but does not exert any force on the distal slider 60 and aproximal position wherein the stop 40 abuts, but does not exert anysignificant force on, the proximal slider 65. This allows the filter 50(or any other functional element which is carried by the mandrel) to befairly precisely positioned within a patient's vessel and retain thatposition even if the guidewire is moved slightly during use. This can beadvantageous in circumstances where other devices are exchanged over theguidewire (e.g., during angioplasty and atherectomy procedures).

The inner diameter of the generally annular collars defining the sliders60, 65 is desirably larger than the outer diameter of the mandrel, asmentioned above. However, the inner diameter of these sliders should besmaller than the outer diameter of the stop 40. In this fashion, thestop serves to limit movement of the sliders. As a consequence, the stop40 serves as an effective limit on proximal movement of the distalslider 60 and distal movement of the proximal slider 65. Apart from thisrelationship with the slider 40 and the fact that both sliders areindirectly linked to one another by the body 52 of the filter, theproximal and distal sliders are slidable along the mandrel essentiallyindependently of one another.

The advantage of this arrangement is illustrated in FIGS. 4 and 5. InFIG. 4, the mandrel 20 is being urged distally (to the left in thisview, as illustrated by the arrow) and urges distally against the distalslider 60. This exerts a distal biasing force against the distal end ofthe body 52 of the filter. In theory, if the filter were used in africtionless environment, the filter would travel with the mandrelwithout any appreciable alteration in the shape of the body 52. In mostclinical applications, though, this is not the case. Instead, there istypically some force restraining completely free movement of the filterwithin the channel of the patient's body. As schematically shown in FIG.3, the body 52 of the filter may resiliently expand into physicalcontact with the interior surface of the vessel V. This contact with thevessel wall will tend to hold the filter 50 in place as the stop of themandrel slides proximally and distally between the two sliders 60, 65.When the mandrel is urged distally until it exerts a distal forceagainst the distal slider 60 (as shown in FIG. 4), this force will tendto axially elongate the body 52.

Resilient tubular braids tend to assume a radially reduced profile uponaxial elongation. (This property and some of its implications arediscussed in International Publication No. WO 96/01591, mentionedpreviously. As a consequence, when the mandrel 20 is urged distally topush distally against the distal slider 60, this distal force actsagainst the restorative force of the resilient braid, which wouldotherwise bias the braid into its expanded configuration (FIG. 3). Byovercoming this restorative force with a countervailing distal force,the body 52 will tend to both axially elongate and assume a radiallyreduced profile. This, in turn, reduces the force with which the bodyengages the wall of the vessel V and reduces friction between the filter50 and the vessel. Hence, urging the mandrel distally to move the filter50 distally will, at the same time, reduce friction between the filterand the vessel wall to further facilitate advancement of the filteralong the vessel's lumen. This requires less force to push the filterdistally, enabling the mandrel to be smaller and reducing the outerdiameter of the collapsed device, making deployment in smaller vesselsfeasible. In addition, the reduced friction between the filter and thevessel wall limits damage to the intima of the vessel, permitting thefilter to be deployed and moved with a minimum of trauma.

FIG. 5 is similar to FIG. 4, but schematically illustrates what happensupon proximal retraction of the mandrel. In this drawing, the stop 40 ofthe mandrel abuts against and exerts a proximal biasing force on, theproximal slider 65 of the filter 50. As discussed above in connectionwith FIG. 4, this proximal biasing force will act against therestorative force of the body 52 to axially elongate and radially reducethat body. This permits the device to be withdrawn proximally along thelumen of the vessel either for repositioning at a more proximal locationor for withdrawal from the patient's body at the end of the procedure.

As can be seen by comparing FIG. 3 with FIGS. 4 and 5, the proximal anddistal sliders 60, 65 are free to move relatively independently of oneanother, limited primarily by their indirect link to one another throughthe body 52 of the filter. For example, when the mandrel 20 is urgeddistally against the distal slider 60 (FIG. 4), the proximal slider willslide proximally along the proximal length 35 of the mandrel. Similarly,when the mandrel is withdrawn proximally to urge proximally against theproximal slider 65, the distal slider will be free to drift distallyalong the distal length 30 of the mandrel. Ideally, there should be asufficient distance between the distal shoulder of the stop 40 and theproximal end of the helical coil 22 at the distal end of the mandrel.

Another salient aspect of the device highlighted in FIGS. 3-5 is thatthe spacing between the sliders 60 and 65 changes in response to themandrel acting against one of the sliders. Looking first at FIG. 3, theproximal and distal sliders are spaced a first distance from oneanother, with the body 52 engaging the wall of the vessel. When the stop40 of the mandrel urges against one of the sliders, though, the body 52will tend to axially elongate and the distance between the two sliderswill increase.

It should be understood that the change in shape between the radiallyexpanded configuration shown in FIG. 3 and the radially reducedconfigurations in FIGS. 4 and 5 has been exaggerated to highlight thischange. For example, in FIGS. 4 and 5, the body 52 of the filter isshown as being spaced completely away from the wall of the vessel. Inmost clinical circumstances, though, the body of the filter will stilltend to at least lightly engage the intima of the vessel and the changein shape of the body likely will be less dramatic.

FIGS. 9 and 10 schematically illustrate certain advantages of thepresent invention when deploying and retrieving the device in a bodychannel using a catheter. FIG. 9 schematically shows the device of FIGS.1-5 being deployed through a catheter C. In particular, a length of themandrel 20 and the entirety of the filter 50 is received within thelumen of the catheter C. The mandrel 20 is being urged distally to exitthe distal end of the catheter C. The stop 40 is exerting a distalbiasing force against the distal slider 60 within the relatively closeconfines of the catheter C. The body 52 of the filter 50 will exert anoutward force against the interior surface of the catheter C, increasingfriction between the filter and the catheter C. The distal biasing forceof the stop 40 acting against the slider 60 will tend to axiallyelongate and radially reduce the body 52 of the filter, thereby reducingfriction between the filter and the catheter C. This can significantlyease the deployment of the device through the catheter C. FIG. 10schematically illustrates retrieval of the device of FIGS. 1-5 and 9which has already been deployed in a patient's vessel. In particular,the filter 50 is being withdrawn proximally into the lumen of thecatheter C. This can be initiated by positioning the distal end of thecatheter C just proximal of the proximal slider 65 and then moving thecatheter C with respect to the stop 40. This can be accomplished eitherby urging the catheter C distally or withdrawing the mandrel 20proximally, as the operator sees fit at the time.

The catheter C will frictionally engage and will tend to radiallycompress the body 52 of the filter. As a consequence, the slider 65 willbe brought in contact with the stop 40. Further movement of the catheterC with respect to the mandrel will urge more of the length of the body52 into the lumen of the catheter C. At the same time, the distal slider60 may slide distally along the distal length 30 of the mandrel,permitting the body 52 to axially elongate in response to the radialcompression induced by the catheter C.

These two figures highlight some of the advantages of this embodiment ofthe invention. In particular, the body 52 of the filter will axiallyelongate and radially reduce in response to movement of the mandrel 20with respect to the catheter C. In deploying the device (FIG. 9), thestop 40 urges distally against the distal slider 60, effectively pushingthe filter 50 distally along the catheter C. In retrieving the device(either for repositioning or for removal from the patient's body), thestop 40 can be seen as pushing proximally on the proximal slider 65.Again, this biasing force will tend to axially elongate and radiallyreduce the body 52 of the filter. This axial elongation and radialreduction of the body 52 in FIGS. 9 and 10 reduces friction with thelumen. In addition, the radial reduction of the body during retrievalinto the catheter C (FIG. 10) facilitates collapse of the filter intothe lumen of the catheter C, making it easier to introduce the filterinto the catheter. This same ability can also be used advantageously ininitially deploying the filter, as explained below.

As noted above, FIGS. 7 and 8 illustrate an alternative embodiment ofthe invention. There are numerous similarities between the device shownin FIGS. 1-6 and that shown in FIGS. 7 and 8. In order to simplifydiscussion, elements in FIGS. 7 and 8 performing a function analogous toan element in FIGS. 1-6 bear the same reference numeral, but incrementedby 100. Hence, FIGS. 1-6 refer to a filter system 10 having a mandrel20; FIGS. 7 and 8 show a filter system 110 having a mandrel 120.

The primary difference between the filter 150 of FIGS. 7 and 8 and thefilter 50 of FIGS. 1-6 is the shape of the filter in its fully radiallyexpanded configuration. The filter 50 has a generally tubular body withspaced-apart tapered ends. In contrast, the filter 150 of FIGS. 7 and 8has a generally umbrella-shaped body 152, with a proximal length of thefabric defining the body being inverted and received within the interiorof the distal portion of the fabric. As a consequence, the distal slider160 and proximal slider 165 are positioned much more closely to oneanother in the fully deployed filter 150, shown in FIG. 7, than are thespacers 60, 65 in the fully deployed filter 50, shown in FIGS. 1-3.

FIG. 8 illustrates the filter 150 in an axially elongated, radiallyreduced state induced by withdrawing the mandrel 120 proximally. Whenthe mandrel 120 is withdrawn proximally within the patient's vessel, thestop 140 will abut and urge proximally against the proximal slider 165.In the embodiment of FIGS. 1-5, 9 and 10, this tends to axially elongatethe body 52 of that filter 50 without any substantial change in theshape of the filter. The filter 150 of FIGS. 7 and 8 is more complex inits fully deployed, expanded state (shown in FIG. 7). Rather than simplyaxially elongating and radially reducing the shape shown in FIG. 7, theproximal length of the fabric which is received within the interior ofthe distal portion of the fabric will tend to evert. The distal portionof the fabric (i.e., the outer portion of the fabric shown in FIG. 7)will tend to remain in place in frictional engagement with the wall ofthe vessel during this process. As a consequence, the shape of theinterior surface of the umbrella will change first without anysignificant change in the external shape.

As the mandrel continues to be withdrawn and the proximal and distalsliders 165, 160 are moved farther apart, the body 152 will take on ashape which looks more like the shape of the filter 50 of the previousembodiment. Continuing to urge proximally against the proximal slider165 will further elongate the body until it reaches a shape such as thatschematically illustrated in FIG. 8. This makes withdrawal of the trapeasier, but care should be taken to ensure that any particular materialretained within the interior of the umbrella-like body 152 is notinadvertently dumped back into the patient's bloodstream. This can bedone, for example, by breaking down trapped thrombus using clot-bustingdrugs or by aspirating the particulate material through a catheterbefore proximally withdrawing the mandrel 120.

In one particularly useful process for withdrawing the deployed filter150 from a patient's bloodstream, a catheter C is urged distally alongthe proximal length 135 of the mandrel until the distal tip of thecatheter (not shown in FIGS. 7 and 8) is positioned in the interior ofthe umbrella-like filter body 152. If necessary, any particulatematerial within that interior can be aspirated through the catheter Cand out of the patient's body. Thereafter, the mandrel can be withdrawnproximally, drawing the proximal slider 165 into the interior of thecatheter C. As discussed above in connection with FIG. 10, this willhelp collapse the body 152 of the filter into the lumen of the catheterC. If so desired, the catheter C can be held in the same position whilethe rest of the filter 150 is drawn inside. Alternatively, the catheterC and the mandrel can be withdrawn together as a unit a short distanceso that the distal tip of the catheter C is positioned slightly proximalof the proximal edge of the deployed filter shown in FIG. 7. This willfurther facilitate drawing the body 152 down into the lumen of thecatheter C. Once at least the majority of the filter 150 is receivedwithin the lumen of the catheter C, the catheter, the filter and themandrel 120 can be withdrawn together as a unit from the patient's body.

FIG. 11 shows a medical device which is similar to the embodiment shownin FIGS. 1-5, 9 and 10. However, the shape of the body 52′ of the plug50′ has a significantly different shape from the body 52 of the filter50 discussed above. Whereas the majority of the length of the filter 50would assume a relatively constant diameter if left unconstrained, thebody 52′ of the plug 50′ has a more complex shape. While this device canalso be used to filter fluid which is passing through a vessel, itsdesign is particularly well-suited to occlude a vessel eithertemporarily or permanently.

A method for making and using a vascular occlusion device having a shapesimilar to that of the body 52′ of FIG. 11 is disclosed in InternationalPublication No. WO 96/01591, the teachings of which were incorporatedabove. Briefly, though, this body 52′ includes a pair of spaced-apartenlarged diameter sections separated by a central section having areduced diameter. If so desired, the surface of this device may becoated with a thrombogenic agent or nylon fibers or the like can beattached to the body 52′. Conversely, if the plug 50′ or the filter 50are to be used solely for purposes of filtering fluids passingtherethrough and it is preferred that any blood passing through thefunctional element not clot thereon, the body can be coated with ananti-thrombogenic agent.

One of the difficulties encountered in using the vascular occlusiondevice disclosed in International Publication No. WO 96/01591 is thefriction between the body of the vascular occlusion device and thecatheter through which it is deployed. The stop 40 urging against thedistal slider 60 of FIG. 11 will tend to axially elongate and radiallyreduce the body 52′ of the plug 50′ as it is urged along the catheter C.This will reduce friction between the plug 50′ and the catheter C,making it significantly easier to deploy the device at the desiredtreatment site. The present design also facilitates repositioning of theplug 50′ if its initial deployment is not precisely at the desiredlocation. In particular, withdrawing the mandrel 20 proximally willexert a proximal biasing force on the proximal slider 65, facilitatingwithdrawal of the device into the deployment catheter, much as discussedabove in connection with FIG. 10. Once the plug is sufficientlyretracted into the catheter, the catheter can be repositioned and theplug can be deployed distally out of the catheter again at the newlocation.

The plug 50′ of FIG. 11 can be used as a temporary occlusion device andwithdrawn at the end of a procedure or treatment course. In othercircumstances, though, it may be preferred to more permanently occludethe channel in which the plug 50′ is deployed. While the stop 40abutting against the sliders 60, 65 facilitates deployment andrepositioning, the attachment of the stop 40 to the mandrel 20 couldeffectively prevent one from removing the mandrel from the plug.

The mandrel 20 can be withdrawn either partially or entirely from theplug in a variety of different manners. For example, the proximalportion 35 of the mandrel can be releasably attached to the stop 40,e.g., by means of a threaded engagement therebetween. Without somehowlocking the distal section 30 against rotation (e.g., by a splinedconnection between the distal section 30 and the distal slider 60),though, it can be difficult to disconnect these parts from one another.

FIG. 12 illustrates one preferred embodiment of a stop 40′ which may beused to withdraw the mandrel 20 while leaving the filter 50 or plug50‘in place in the patient’s body. In the prior embodiments, the stop 40and the proximal slider 65 were both essentially annular in shape, withthe relatively constant outer diameter of the stop being greater thanthe relatively constant inner diameter of the slider. As a consequence,one cannot readily withdraw the stop 40 from within the enclosure of thebody 52 of the filter 50.

The stop 40′ of FIG. 12, however, can be withdrawn from the interior ofa filter 50, plug 50′ or other device having a suitably adapted proximalslider. The stop 40′ includes an external thread 42′ which extendsspirally outwardly from the main body 44′ of the stop. The proximalslider (not shown in this view) has a threaded internal surface which issized and shaped to mate with the outer thread 42′ on the stop 40′.Aside from the spiral slot or keyway shaped to receive the thread 42′ ofthe stop, the inner diameter of the proximal slider should be slightlygreater than the outer diameter of the body 44′ of the stop but lessthan the maximum diameter of the stop including the thread 42′. Duringnormal operation, this will ensure that the stop 40′ will abut againstthe proximal slider so the device will operate as described above.

If an operator decides to leave the filter 50 or plug 50′ in place,though, the mandrel can be withdrawn from the filter or plug by pullingthe mandrel proximally until the stop 40 lightly abuts the proximalslider. Rotating the mandrel about its axis will permit the thread 42′to travel along the slot in the proximal slider. In this manner, thestop can be withdrawn through the proximal slider and the mandrel can becompletely removed from the patient's body, leaving the medical devicein place within the vessel.

The present invention also contemplates a method of employing a medicaldevice in a channel in a patient's body. For the sake of convenience,the following discussion will make reference to FIG. 1-5 and thereference numbers used therein. It should be understood, though, thatthis method can be used with any of a wide variety of medical deviceshaving different functional elements (including the plug 50′ and thedrainage catheter 250 illustrated in other drawings) and need not belimited to a filter system 10 having a filter 50 as its functionalelement.

In accordance with this method, the medical device is introduced into avessel in a patient's body. In the medical device 10 shown in FIGS. 1-5,this would comprise inserting the distal end 25 of the mandrel 20 intothe lumen of the patient's vessel V. This may be done either directlyor, more commonly, by using an introducer sheath. Such introducersheaths are commonly used in introducing medical devices for minimallyinvasive procedures. Once the mandrel is introduced into the vessel, themandrel can be urged distally to introduce the functional element, i.e.,filter 50 in FIGS. 1-5, and to the vessel, as well. Using the filtersystem 10 of FIGS. 1-5, this can be accomplished simply by urging themandrel distally and allowing both the action of the stop 40 against thedistal slider 60 and the contact with the wall of the introducer sheathto collapse the filter body 50 into a radially reduced configuration.The same tendency of the filter body 52 to axially elongate and radiallyreduce discussed above in connection with FIG. 4 will also reducefriction between the filter body 52 and the interior surface of theintroducer sheath as the filter is advanced therealong.

The filter 50 may be urged distally along the lumen of the vessel V to apredetermined treatment site. The treatment site may, for example,simply be a convenient location in a patient's vasculature positioneddistally of an obstruction which will be treated with an angioplastyballoon or an atherectomy device. As explained above, the filter 50 canbe advanced along the vessel by urging the mandrel distally such thatthe stop 40 engages the distal slider 60. This exerts a distal biasingforce on the distal slider which, in turn, acts against a restorativeforce of the body 52 of the filter. As a result, the body 52 will tendto axially elongate and take on a radially reduced profile. This reducesfriction between the filter 50 and the wall of the vessel, facilitatingadvancement therealong.

Once the filter has reached the desired treatment site, the axial forceagainst the mandrel can simply be released. This will permit the body 52to expand radially and axially contract, drawing the two sliders 60, 65toward one another along the mandrel. If it is determined that thefilter is not precisely positioned in the desired treatment site, it canbe readily repositioned by pushing the mandrel distally or withdrawingit proximally and again allowing the filter to self-expand radially andself-contract axially once the mandrel stops acting against the sliders.When it comes time to remove the filter 50 from the patient's vessel ormove it proximally to a new treatment site, the operator can simply pullproximally on the mandrel to radially contract the device and facilitateproximal movement within the vessel, as shown in FIG. 5.

In some circumstances, one may wish to limit the trauma to the intima ofthe vessel walls which may otherwise occur as the filter 50 is draggedalong the vessel to the desired treatment site. This can be accomplishedusing a catheter to position the device adjacent the desired treatmentsite and/or to withdraw the device from the vessel after it has beendeployed.

In accordance with one such method, a catheter may be positionedadjacent a treatment site in a patient's body. This can be done in anydesired fashion. For example, the mandrel 20 and the catheter can beadvanced simultaneously through the patient's vessel. In a particularlypreferred embodiment, though, the catheter will be positioned at thedesired treatment site before the mandrel 20 is inserted into thecatheter. This permits the operator to steer the catheter into placewithout hindrance from the mandrel or to track the catheter over aguidewire if the desired treatment site is positioned in a narrower ormore tortuous vessel, after which the guidewire can be removed.

Once the distal tip of the catheter is positioned adjacent the treatmentsite, the distal tip 25 of the mandrel can be inserted into the proximalend (not shown) of the catheter outside the patient's body. Once thedistal slider 60 of the filter 50 enters the proximal end of thecatheter, the catheter will frictionally engage the body 52 of thefilter. Further distal urging of the mandrel will cause the stop 40 toexert a distal biasing force on the distal slider 60. Much like theprocess shown in FIG. 10, this distal biasing force will tend to axiallyelongate and radially reduce the body 52, further facilitating entry ofthe body into the lumen of the catheter.

Once the filter 50 is received within the catheter, it may continue tobe urged distally along the length of the catheter. As explained abovein connection with FIG. 9, the distal urging of the stop 40 against thedistal slider 60 will axially elongate and radially reduce the body,reducing friction between the body and the catheter during suchadvancement. If the distal tip of the catheter is positioned justproximally of the desired treatment site, the mandrel can be urgeddistally until the device exits the distal end of the catheter.Preferably, the body will then tend to radially self-expand until itreaches a radially-expanded shape wherein it may engage the walls of thevessel (B in FIG. 9). Alternatively, the distal tip of the catheter maybe positioned distally of the desired treatment site. In such acircumstance, advancement of the mandrel can be stopped when theoperator determines by means of the radiopaque sliders 60, 65 that thefilter is in the desired treatment site. Thereafter, the catheter can bewithdrawn proximally while holding the mandrel 20 in place. As thedistal tip of the catheter is withdrawn proximally from the body 52 ofthe device, the body will tend to radially self-expand with the distalslider 60 remaining in substantially the same place due to its abutmentagainst the stop 40.

In many circumstances, one may wish to deploy the filter 50 in atemporary fashion so that it may be readily withdrawn in the mannerdiscussed below. In other circumstances, though, it may be desirable toleave the device in place in the patient's body for an extended periodof time or even permanently. This is the most likely scenario for a plug50 deployed in a patient's vascular system as a vascular occlusiondevice, for example.

It is preferred that the mandrel be withdrawn from the patient's bodyeither in part or in its entirety. By establishing a selectivelydisengageable connection between one length of the mandrel and anotherlength, the distal most of those lengths can be detached from oneanother, leaving the filter 50 and the distal-most length in thepatient's body while withdrawing the proximal-most length. These lengthscan be connected in any fashion known in the art, such as by means of athreaded engagement or by means of a solder which can be melted orsoftened by application of electrical resistance heating of the mandrel.

More preferably, though, the entire mandrel 20 is withdrawn from thepatient's body. This can be done by withdrawing the stop 40 through theproximal slider 65 of the filter. One suitable stop 40′ is shown in FIG.12. This stop 40′, used in conjunction with a specially adapted proximalslider (not shown, but described above) can be used to withdraw the stopthrough the proximal slider for removal of the mandrel. As explainedpreviously, this can be accomplished by bringing the stop 40′ intoabutting engagement with the proximal slider then rotating the mandrel20 about its axis. This will cause the thread 42′ extending radiallyoutwardly from the body 44′ of the stop to pass along a mating slot inthe proximal slider. After the mandrel has been rotated sufficiently tocompletely withdraw the stop through the proximal slider, the mandrelcan easily be withdrawn from the body by withdrawing the distal portion30 of the mandrel proximally through the center of the filter body 52and out of the patient's body entirely.

If the device is not to be permanently left in its original position,one can withdraw the filter 50 from the body by withdrawing it into thelumen of the catheter C. This can be done either to withdraw the filter50 from the patient's body at the end of a procedure or simply forpurposes of repositioning the filter at a new location. As discussedabove in more detail in connection with FIG. 10, the filter 50 can bewithdrawn into the lumen of the catheter C either by holding the mandrelstationary and advancing the catheter distally over the filter 50 or byholding the catheter in a fixed position and withdrawing the mandrel 20proximally. Either way, the proximal urging of the stop 40 against theproximal slider 65 tends to axially elongate and radially reduce thebody 52, both facilitating entry of the body 52 into the lumen of thecatheter and reducing friction between the catheter and the length ofthe body 52 which is already received therein. Once the filter 50 isreceived within the catheter, the catheter may be held in place and themandrel 20 and filter 50 can be completely removed from the catheter.Alternatively, the catheter, mandrel and filter 50 can all be removedsimultaneously as a unit from the patient's body.

While a preferred embodiment of the present invention has beendescribed, it should be understood that various changes, adaptations andmodifications may be made therein without departing from the spirit ofthe invention and the scope of the appended claims.

1. A collapsible medical device comprising: a) a mandrel having a distalend and a stop spaced proximally of the distal end, a proximal length ofthe mandrel extending proximally of the stop and a distal length of themandrel extending distally of the stop; and b) a functional elementcomprising a radially expandable body having a proximal slider and adistal slider, the proximal slider being slidably carried along theproximal length of the mandrel and the distal slider being slidablycarried along the distal length of the mandrel, the proximal and distalsliders being slidable along the mandrel independently of one anothersuch that the distance between the proximal slider and distal slider canbe varied to effect different configurations of the functional element.2. The medical device of claim 1 wherein the functional element has anexpanded configuration and is capable of being collapsed for passagealong a lumen, the functional element being adapted to resilientlyreturn toward the expanded configuration in the absence of any biasingforce.
 3. The medical device of claim 1 wherein the body of thefunctional element assumes a radially reduced configuration when thedistance between the proximal slider and the distal slider is increased.4. The medical device of claim 3 wherein the stop abuts the proximalslider and exerts a proximal biasing force thereon, such proximalbiasing force acting against a restorative force of the body to axiallyelongate and radially reduce the body.
 5. The medical device of claim 3wherein the stop abuts the distal slider and exerts a distal biasingforce thereon, such distal biasing force acting against a restorativeforce of the body to axially elongate and radially reduce the body. 6.The medical device of claim 1 further comprising a control sheath, thebody being collapsed within the sheath with the proximal and distalsliders spaced from one another.
 7. The medical device of claim 5wherein a wall of the control sheath exerts a biasing force against aradially restorative force of the body, such biasing force maintaining aspace between the proximal and distal sliders.
 8. A collapsible medicaldevice comprising: a) a mandrel having a distal end and a stop spacedproximally of the distal end, a proximal length of the mandrel extendingproximally of the stop and a distal length of the mandrel extendingdistally of the stop; and b) a functional element comprising a radiallyexpandable body having a radially expanded configuration and adapted toresiliently assume the radially expanded configuration in the absence ofa countervailing biasing force, the body being attached to the mandrelby a proximal slider and a distal slider, the proximal slider beingslidably carried along the proximal length of the mandrel and the distalslider being slidably carried along the distal length of the mandrel,the proximal and distal sliders being slidable along the mandrelindependently of one another such that the distance between the proximalslider and distal slider can be varied to effect differentconfigurations of the body.
 9. A collapsible medical device comprising:a) a mandrel having a distal end and a stop spaced proximally of thedistal end, a proximal length of the mandrel extending proximally of thestop and a distal length of the mandrel extending distally of the stop;and b) a functional element formed of a resilient tubular braid whichhas a preferred radially expanded configuration but will assume aradially reduced profile upon axial elongation, proximal and distalsliders being attached to the tubular braid with a length of the braidextending therebetween, the proximal slider being slidably carried alongthe proximal length of the mandrel and the distal slider being slidablycarried along the distal length of the mandrel, the proximal and distalsliders being slidable along the mandrel independently of one another.10. The medical device of claim 9 wherein the stop has an externaldiameter larger than an internal diameter of either the proximal slideror the distal slider.
 11. The medical device of claim 9 wherein the stopis sized to urge distally against the distal slider upon distal urgingof the mandrel, such distal urging thereby axially elongating thefunctional element to facilitate its advancement along a lumen.
 12. Afilter system for temporary deployment in a channel of a patient's body,comprising: a) a mandrel having a distal end and an enlarged diameterstop spaced proximally of the distal end; and b) a filter formed of aresilient tubular braid and including proximal and distal sliders, theproximal slider being slidably carried along the mandrel proximally ofthe stop and the distal slider being carried along the mandrel betweenthe stop and the distal end of the mandrel, the filter having acollapsed configuration wherein the sliders are spaced from one anothera first distance along the mandrel and the filter has a first diameter,and an expanded configuration wherein the sliders are spaced a second,shorter distance along the mandrel and the filter has a second diameter,the first diameter being less than the second diameter.
 13. The filterof claim 12 wherein each of the proximal and distal sliders comprises anannular collar having an inner diameter larger than an outer diameter ofthe mandrel but smaller than an outer diameter of the stop, the stopthereby serving to limit movement of the sliders.
 14. The filter ofclaim 12 wherein the proximal and distal sliders are slidable along themandrel independently of one another.
 15. The filter of claim 12 whereinthe stop abuts the proximal slider and exerts a proximal biasing forcethereon, such proximal biasing force acting against a restorative forceof the filter to axially elongate and radially reduce the filter. 16.The filter of claim 12 wherein the stop abuts the distal slider andexerts a distal biasing force thereon, such distal biasing force actingagainst a restorative force of the filter to axially elongate andradially reduce the filter.
 17. A method of employing a medical devicein a lumen of a vessel, comprising: a) providing a collapsible medicaldevice comprising a mandrel having a distal end and a stop spacedproximally of the distal end; and a functional element formed of aresilient tubular braid and including proximal and distal sliders, theproximal slider being slidably carried along the mandrel proximally ofthe stop and the distal slider being carried along the mandrel betweenthe stop and the distal end of the mandrel; b) inserting the distal endof the mandrel in the lumen and urging the functional element distallyalong the lumen to a treatment site by urging the mandrel distally suchthat the stop engages the distal slider and exerts a distal biasingforce thereon, such distal biasing force acting against a restorativeforce of the functional element to axially elongate the functionalelement and reduce friction between the functional element and a wall ofthe vessel.
 18. The method of claim 17 wherein the proximal slider anddistal slider are permitted to slide along the mandrel independently ofone another.
 19. The method of claim 17 further comprising allowing thefunctional element to resiliently self-expand radially and self-contractaxially by ceasing the distal urging of the mandrel when the functionalelement reaches the treatment site.
 20. The method of claim 17 or claim19 further comprising moving the functional element proximally along thelumen by withdrawing the mandrel proximally such that the stop engagesthe proximal slider and exerts a proximal biasing force thereon, suchproximal biasing force acting against a restorative force of the filterto axially elongate the filter and reduce friction between thefunctional element and the wall of the vessel.